Copidozoum rhoae Yang, Seo and Gordon, 2018

Copidozoum rhoae Yang, Seo and Gordon, 2018

Figure 4 View FIGURE 4

v. 2018 Copidozoum rhoae Yang, Seo and Gordon , p. 496, figs. 2–5.

Figured material. PMC EDM-Collection

J.H.B.122a, sample 19033 ( Figure 4A–B View FIGURE 4 ), sample

19017 ( Figure 4C View FIGURE 4 ), and sample 19021 ( Figure 4D View FIGURE 4 );

Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Description. Colony encrusting, multiserial, unilaminar. Autozooids distinct, delineated by deep interzooidal furrows, variably shaped, ranging from oval to elliptical, or irregularly lozenge- or pear-shaped, longer than wide (mean ZL/ZW 1.56). Gymnocyst smooth and convex, most extensive proximally, tapering laterally and distally, accommodating 12–17 circumopesial spines (with an average of 15±2), constantly 12 in zooid distal to ovicellate zooids; spine bases 20–27 µm in diameter (with an average of 23±2 µm), with the second distalmost pair having a larger diameter of 27–41 µm (with an average of 33±4 µm). Cryptocyst forming a raised beaded rim, with rim granules measuring 7–9 µm in diameter, sloping inwards to create an extensive, depressed, flat shelf, transitioning from coarse granular proximally to progressively smooth towards the proximal margin of the opesia. Opesia ovoidal to bell-shaped, slightly longer than wide, occupying slightly less than half of the zooidal surface (mean OpL/ZL 0.41). Avicularia subvicarious, large, slightly over half the size of an autozooid, resting on a convex cystid of smooth gymnocyst, scimitar-shaped, with a rounded rostrum measuring 206–240 µm in length (with an average of 223±17 µm); rostrum tip slightly curved on one side, directed distally, opesia elongate and figure eight-shaped, palate extensive and smooth, condyles robust. Ovicells hyperstomial, globular; endooecium coarsely granular (granule diameter 8–21 µm), ectooecium mostly uncalcified except for a narrow peripheral band, 16–18 µm wide, of smooth calcification forming an acute distal spike, 40–56 µm high, and proximal raised convolutions. Mid-distal, elliptical pore-chamber windows observed, c. 30 µm long by 60 µm wide.

Measurements (µm). ZL 472±41, 416–513 (3, 7); ZW 303±16, 277–327 (3, 7); CryL 181±36, 96–223 (3, 12); GymL 77±21, 49–118 (3, 10); OpL 194±21, 169–230 (3, 7); OpW 170±16, 151–197 (3, 7); AvCyL 324±12, 313–337 (2, 3); AvCyW 212±25, 193–240 (2, 3); AvL 282±18, 266–301 (2, 3); AvW 129±4, 127–134 (2, 3); AvOpL 118±7, 110–124 (2, 3); AvOpL 42±8, 33–47 (2, 3); OvL 201±20, 182– 234 (3, 8); OvW 235±28, 186–273 (3, 8).

Remarks. Copidozoum rhoae stands out as one of the commonest components of the bryozoan assemblage in the Daidokutsu cave core. Specimens have larger autozooids and avicularia compared to the Recent material described from South Korea by Yang et al. (2018). Our morphological measurements closely align with those given in the original description of Copidozoum kikaijimense Kataoka, 1961 , a Pleistocene Japanese species found in the Ryukyu Limestone of Kagoshima Prefecture, Japan. This species also bears a striking resemblance to C. rhoae , except for the ovicell, which is described as smooth, the presence of septula as interzooidal communications, and the smaller size of the avicularia. Unfortunately, the poor quality of the image in Kataoka (1961) prevents a more certain comparison between Copidozoum kikaijimense and specimens of C. rhoae from both Japan and South Korea.